The biological effect of X-ray and carbon ion beam on different MGMT status glioma cells treated by TMZ and O6-BGThe biological effect of X-ray and carbon ion beam on different MGMT status glioma cells treated by TMZ and O6-BG

Object: To find the effect of X-ray and carbon ion beam on survival, cell cycle change, invasion and migration abilities of different O6-methylguanine–DNA methyltransferase (MGMT) status glioma cells (T98G and A172) treated by temozolomide (TMZ) and O6-benzylguanine(O6-BG), a MGMT inhibitor. Materials and methods: Human glioma cell lines T98G (MGMT+) and A172 (MGMT-) were treated by TMZ and O6-BG for 72 hours before exposed to different doses of X-ray and carbon ion beam on the fourth day. Colony assay and transwell method was used for analyzed survival rates and migration/invasion ability. Cell cycle distribution was measured by flow cytometry. Results: TMZ and O6-BG combined treatment with irradiation showed additive cytotoxic effects for both cell lines. For T98G, not A172, radiosensitization effect was found after exposure of X-ray and carbon ion beam. After treated by drugs, the ratio of G2/M to G1 phase of T98G was significantly higher than that in A172. With or without drug treatment, the migration and invasion ability of either cell lines did not show any difference after irradiated by X-ray or carbon ion beam. Conclusion: This is the first report that find radiosensitization effect of carbon ion beam exposure to T98G, which is resistant to radiation and TMZ. The probable mechanism is the cell cycle distribution change after treated by TMZ and O6-BG as the G2/M phase is more sensitive to radiation. Further research should be carried to find optimized combination of carbon ion beam and chemotherapy for glioma cells.55th PTCOG